Electron discharge tube



July 1, 1958 G. RYBAKoFF ELECTRON DISCHARGE TUBE Filed March 15, 1955 /llli- A l 1 l/ m in 5 3 0| 2 l 2 3 m 2 ndi- 66 444 32 O .N

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lNvENToR GEORGE RYBAKOFF BY M W57/ AGENT `shell forming a part ofthe envelope of the tube.

United States Patent j 2,841,735 y ELECTRON DISCHARGE TUBE `George Rybakol, Little Neck,lN. Y., assigner, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application March 15, 1955, Serial No. 494,356

3 Claims. (Cl. 313-242) This invention relates to electron discharge tubes, and, in particular, to electron discharge tubes of the rectiiier type.

`One object of the invention is to provide la miniature, ruggedized, high-vacuum, diode-rectier tube Another object ofthe invention is to produce an inherently small, external anode, liquid-immersion type of rectilier tube capable of handling a comparatively large amount of power for its size. i

A 'further object of the invention is to provide `a tube of the foregoing type adapted for mounting in a fusetype plug-in-structure or `socket and where the anode serves as the prime means of tube support.

lStill a further object of the invention is to provide a miniature vacuum diode suitable for liquid immersion or other type of forced or static cooling and capable of dissipating comparatively high quantities of power under adverse conditions of temperature and mechanical `shock and vibration.

Another object of the invention yis -a tube of the lforegoing type `which lis capable of mass-production at low cost.

These and other objects of 'the invention will be best understood from the following description, taken in connection 4with the accompanying drawing, wherein:

nEig. `l is a cross-sectional view of one form of discharge tube in accordance with the invention;

iFig. 2 is a cross-sectional view of another torm of tube in accordance with the invention;

f Figs. 3a and 3b are views showing fthe tube of Fig. l mounted in a socket.

`Referring now to the drawing, Fig. l shows `one construction of the invention whereby the desired objects are attained. Thewtube shown, which is of the diode type, comprises an external, metal anode and `an indirectlyheated cathode 11, The anode l10, which may be constituted of copper, comprises arelatively strong, rigid it in cludes a cylindrical portion 12 integral with a domeshaped portion 13, both symmetrical about :the central axis of the tube designated by 115. The `cathode 11 may be ofthe oxide-type and comprises, ttor example, a closed* oft nickel tube 16 coated 'with a mixture of barium and strontium carbonates 17 to enhance electron emission. As |will be observed, 'the external contour of the cathode `11 is identical, though on `a smaller scale, `w-ith the internal contour of the anode 10. Thus, the cathode also has cylindrical and dome-shaped integral portions, both of which are capable of emitting electrons, and is mounted concentrically with regard `to the anode. By this geometry, the spacing between the cathode and anode along their entire active surfaces is the same, 4thereby maintaining a uniform voltage gradient therebetween at all times and enabling the fullest use to be made of the 'available cathode and anode surface area. This feature of the invention is important since it enables the dimensions of the tube to be markedly reduced by means of this yICC electrode geometry which maximizes the electron emitting and receiving surfaces.

The cathode 11 is maintained at electron-emitting temperature by a heating-coil 20 mounted therewithin. To this end, the nickel tube 16 is closed oit by a metal, e, g., nickel, member 21 secured to the tube 116 and to a conductive support rod ZZ, one end of which is connected to one, the upper, terminal of the heater 20. Thus, the cathode 11 `and one end of `the heater 20 are electrically connected together via the common conducting rod 22. An insulating sleeve 23 is mounted on the member 21. Through the center `of `this -sleeve 23, Iand thus insulated `from Ithe cathode 11, passes a lead from the second conducting rod 24 connected to the bottom or still unconnected end of the heater 20. The two rods 22, `24 are maintained in their spaced, insulated relationship by -a ceramic `support I26 having three equi-spaced bores therein arranged yabout 'the central axis thereof. The third bore contains a dummy lead 28. The three leads v22, 24 and 28 are then secured each to a separate terminal 29, 30, 31 vacuum-tight sealed into the base 32 `of the tube. The construction ythus obtained results in =a three-pin standard input connection for the tube. By means of lan exhaust tabulation 34 in the 'base `ft2, the interior of the tube may be evacuated in the conventional manner.

The remainder of the envelope of 4the tube is constituted by a cylindrical vitreous portion 35, e. g., a bor-osilicate glass or a ceramic body, and an annular member 36, e. g., of Kovar, sealed to the vitreous portion. The member 36 has a reentrant portion constricting `the tube volume between the anode 10 and the vitreous base portion 35. Kovar has the composition of approximately 29% nickel, 17% cobalt, 0.3% manganese, and :the remainder iron, and is readily sealed tothe usual borosilicate glass having about the same expansion coellicient. As shown, fthe Kovar annular member or ring 36 is sealed to the vitreous mem-'ber 35 at one end, and is 'brazed to the copper Ianode 10 at `the other end. All joints are vacuum-tight and completely seal ott lthe interior of fthe tube.

The envelope construction just described constitutes an important feature of the invention. As will be observed, the envelope of the tube is `constituted ot a vitreous base portion 35, a reentrant ring portion 36 sealed to the base, and the external anode 10 sealed to the ring 36. This construction offers the advantages of simplicity, ease of manufacture, ruggedness, and inexpensiveness. Two fur* ther important advantages obtain `from 'the configuration of the reentrant ring portion 36. It will be observed that the reentrant ring, as a constriction, serves to divide or restrict the tube into two portions. The first 'or upper half contains the electron emitting and receiving portions,

.whereas the second or lower half contains the base and input section. The reentrant ring, lying therebetween, serves as a barrier or` shield against the radiation of heat and the` passage of electrons from the upper to the lower half of the tube. lIn the `former capacity as a heat shield, it enables operation of the heater yat a lower power while still maintaining the desired temperature of `the cathode since less heat escapes to `the bottom of the tube, pro ducing an important saving in input power. In the latter capacityas `a barrier `against electrons, it prevents the seal between the ring 3'6 and the vitreous portion 35, as well asthe remaining portions of the vitreous member, ,from being bombarded by electrons and possibly deteriorating, cracking or puncturing as a consequence. in sum, therefore, the reentraut ring 36 serves the functions of torming part of the envelope, enabling sealing of the metal anode to the vitreous base, confining the heat in the upper half of the tube to conserve power, and preventing electron bombardment of the vitreous portion.

The usual getter 40 may be mounted in the lower half of the tube. It comprises, for example, a member 41 consisting of a suitable getter material, e. g. barium-aluminum. The getter is electrically connected by welded leads 42 between the pins 29 and 31. Heating ofthe getter in the usual way enables residual gases in the 'tube to be tied up by the -vaporizing getter material.

Fig. 2 illustrates another form of tube construction by which the desired results may be attained. In this embodiment, the reentrant metal ring 50 has a slightly different shape from that of Fig. l. In particular, in Fig. 1, the ring 36has a cylindrical lower portion with a transversely extending ange at the top brazed along its periphery to the anode 10. The bottom of the ring, in turn, is sealed to a reentrant portion of the vitreous member 35. In Fig. 2, on the other hand, the bottom vitreous portion 51 is cylindrical only with no reentrant portion. However, the Kovar ring 50, which is sealed to the member 51 and the anode 10, has the shape illustrated, which may be likened to a cylindrical half-torus section, to en able sealing at both ends to the anode and vitreous portion as required.

The input section of the tube of Fig. 2 is also different from that of Fig. 1 and constitutes a coaxial input. It comprises, in particular, an outer cylindrical conductor 53 sealed in the base and electrically connected by the lead 54 to one end of the heater 20, and an inner, also cylindrical conductor 55 sealed in the base and electrically connected via the lead 56 to the cathode 11 and the other end of the heater 20. The inner conductor 55' is closed off by a metal cap 57. The exhaust tuhulationl on the tube illustrated in Fig. 2 is located at the top of the anode 10. It comprises a pinched-off metal tubing 59 which is ultimately covered with a metal protective cap 60. The provision of the exhaust tubulation at this location on the anode does not substantially interfere with the eld gradiant in the anode-cathode space.

Fig. 3 illustrates the tube of Fig. 1 mounted in a lockin type of tuse socket 65. As will be observed, the fuse clip 66 tightly embraces practically all of the external anode 1t) and rigidly holds it in position. Thus, the anode supports the entire tube. Further, the anode 10 is in intimate mechanical and electrical Contact with the fuse clip 66, and this latter member thus can serve, in addition to its electrical and mechanical functions, as an additional conductor and radiator, i. e., dissipator, of the heat generated at the anode. The input connections can then be made directly to the exposed tube terminals as shown. In operation, the tube as shown may be operated completely submerged in insulating oil, which thus directly contacts the external anode 10 and the supporting fuse clip 66 and enables a maximum dissipation of heat. It will be noted that the anode 10 is locked in place by the tabs 67 which engage the reentrant portion of the annular member 36, as well as the dome-shaped end of the anode 10.

To illustrate the excellent operation attained with tubes of the type described above, there follows below a detailed description of one such tube made as shown in Fig. 1. The overall height of the tube was 2 inches. The diameter of the anode 10 was :'t of an inch and that of the constricted portion 1A. of an inch. The height of the anode 10 was 1 and 1A; inches. As a rectifier, the filament was rated at 6.3 volts and 1 and 1/2 amps. The operating potentials were 16 kilovolts, for which the average current was 70 milliamperes and the peak current 275 milliamperes, thereby expending a comparatively high amount of power in view of the small dimensions of the tube. The tube was subjected to extensive shock and vibration without having any of its characteristics altered in the very least. In connection with liquid im* mersion cooling in insulating oil, the tube of the invention can operate at peak ratings at an ambient oil temperature range of 65 C. to -|-165 C. without any adverse eifects appearing.

While we have described our invention in connection with specific embodiments and applications, other modications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. An electron discharge device comprising an evacuated envelope, said envelope including an external metal anode, a vitreous base portion spaced from said anode, and an intermediate annular member having a reentrant portion constricting the space communicating with both the anode and the base and constituting part of the envelope, a cathode within said anode, said cathode having surface portions spaced equal distances fromV corresponding portions of the anode whereby a uniform voltage gradient is maintained therebetween, and terminal connections for such cathode extending through said reentrant portion to said base whereby said annular member shields said base from destructive electron ilow from said cathode.

2. An electron discharge tube comprising an evacuated envelope, said envelope including an external cylindrical metal anode, a glass base portion spaced from one end of said cylindrical anode, an intermediate annular metal member, having a reentrant portion constricting the space communicating with both the anode and the base portion, said annular member constituting part of the envelope and vacuum-tight sealed to said anode and base, a cylindrical cathode mounted substantially concentrically within said anode, and terminal connections for said cathode extending through and sealed into said base, said annular member shielding saidbase from excessive flow of electrons from said cathode.

3. An electron discharge device comprising an evacuated envelope, said envelope including an external metal anode having a cylindrical portion and a dome-shaped end portion closing one end of said cylindrical portion, a vitreous base spaced from the other end of said'anode, and an intermediate annular metal member between said base and said anode, said annular member having a reentrant portion constricting the space communicating with both the anode and the base and constituting part of the envelope, a cathode mounted concentrically within said anode and also having integral electron emissive cylindrical and dome-shaped portions substantially equally spaced from corresponding portions of said anode, and terminal connections for Said cathode extending through and sealed into said base, said reentrant portion shielding said base from destructive current flow from said cathode.

References Cited in the file of this patent UNITED STATES PATENTS 1,661,436 McCullough Mar. 6, 1928 1,790,152 Hull Jan. 27, 1931 1,874,753 Hull Aug. 30, 1932 2,310,147 Dailey Feb. 2, 1943 2,431,144 Scullin Nov. 18, 1947 2,569,847 Eitel et al. Oct. 2, 1951 FOREIGN PATENTS 640,239 Great Britain July 12, 1950 

